Various types of bandages and wound dressings are known and used to protect wounds, burns and blisters. Typically, wound dressings are fabricated with an absorbent material so that wound exudate is removed and the wound dries, facilitating healing. Wound dressings may also contain one or more pharmacologically active agents such as antibiotics, local anesthetics, or the like. Commonly used wound dressings include fibrous materials such as gauze and cotton pads, which are advantageous in that they are absorbent but problematic in that fibers may adhere to the wound or newly forming tissue, causing wound injury upon removal. Other wound dressings have been prepared with foams and sponges, but the absorbance of these materials is often limited. Furthermore, such wound dressings require the use of adhesive tape, as they are not themselves adhesive. Finally, many of these wound dressings are not translucent or transparent, thus rendering it difficult to monitor healing without removal of the dressing.
To improve the absorbance of conventional fibrous wound dressings, water-swellable polymers or “hydrogels” have been incorporated into gauze or other fibrous materials for application to a wound. For example, U.S. Pat. No. 5,527,271 to Shah, et al. describes a composite material made from a fibrous material, such as cotton gauze, impregnated with a thermoplastic hydrogel-forming copolymer containing both hydrophilic and hydrophobic segments. While the wound dressings are described as having increased absorptive capacity, the adhesion of fibers to the wound or newly forming tissue remains a significant disadvantage.
Another approach has been to use water-swellable polymeric materials instead of gauze, cotton, and the like. Wound-contacting surfaces made of such materials are not only more absorbent than conventional fibrous materials, they are also advantageous in that there is no risk of fiber adhesion during wound healing and upon removal of the wound dressing. Such wound dressings are disclosed, for example, in U.S. Pat. No. 4,867,748 to Samuelsen, which describes the use of an absorbent wound-contacting composition made from a water-soluble or water-swellable hydrocolloid blended with or dispersed in a water-insoluble, viscous, elastomeric binder. U.S. Pat. No. 4,231,369 to Sorensen et al. describes “hydrocolloid plasters” as sealing materials for ostomy devices, the materials consisting of a continuous hydrophobic phase made from a hydrophobic pressure-sensitive adhesive, an elastomeric plasticizer, and a tackifying resin, with a discontinuous phase dispersed therein consisting of a water-soluble or water-swellable polymer. Such plasters are also described in U.S. Pat. No. 5,643,187 to Naestoft et al. U.S. Pat. No. 6,201,164 to Wulff et al. describes a somewhat different type of hydrocolloid wound gel, consisting of a water-insoluble, water-swellable, crosslinked cellulose derivative, an alginate, and water.
Hydrogel bandages have also been employed in wound dressings, as described, for example, in U.S. Pat. No. 4,093,673 to Chang et al. Hydrogel bandages are made from a liquid absorbing crosslinked polymer and have a high water content prior to use. The high water content causes the hydrogel to exhibit very little or no adhesion, requiring the use of adhesive tape or a plaster such as 2nd Skin® dressing available from Spenco Medical Ltd., U.K.
However, in spite of the advances in the art, numerous problems continue to be encountered with gel-based wound dressings made with hydrocolloids and hydrogels. The reason for this is, in part, that there are conflicting requirements for an ideal material. The material should not be so adhesive that it tends to adhere to a wound and thus cause pain or further injury upon removal. However a wound dressing should adhere sufficiently to a body surface so that separate adhesive tapes and adhesive plasters are not necessary. Peripheral adhesives can be used, but require an additional manufacturing step. In addition, a wound dressing should conform to the contours of the skin or other body surface, both during motion and at rest. For wound dressings that also serve as a cushioning pad, higher cohesive strength materials should be used, without any loss in adhesion.
Many of these problems are addressed by the adhesive compositions described in U.S. patent application Publication No. 2003/0170308 to Cleary et al. and U.S. patent application Publication No. 2003/0225356 to Kulichikhin et al. However, in spite of these advances in the art, there remains a need for self adhering dressings which provide instant tack and prolonged skin adhesion, greater fluid handling capability, higher cohesive strength, decreased cold flow, less erosion, controlled active delivery, ease of manufacturability, and translucency. The present invention addresses those needs, and provides for formulations having increased resistance to cold flow and better tackiness to dry skin, as compared to the formulations described in U.S. patent application Publication No. 2003/0170308. The formulations described in U.S. patent application Publication No. 2003/0225356 also have such properties, but the instant formulations provide for higher moisture uptake without the loss of adhesion.